Patient interfaces, such as masks for covering the mouth and/or nose, are used for delivering gas to a patient. Such gases, like air, cleaned air, oxygen, or any modification of the latter, are submitted to the patient via the patient interface in a pressurized or unpressurized way.
For several chronic disorders and diseases, a long-term attachment of such a patient interface to a patient is necessary or at least advisable.
One non-limiting example for such a disease is obstructive sleep apnoea or obstructive sleep apnoea syndrome (OSA). OSA is usually caused by an obstruction of the upper airway. It is characterized by repetitive pauses in breathing during sleep and is usually associated with a reduction in blood oxygen saturation. These pauses in breathing, called apnoeas, typically last 20 to 40 seconds. The obstruction of the upper airway is usually caused by reduced muscle tonus of the body that occurs during sleep. The human airway is composed of walls of soft tissue which can collapse and thereby obstruct breathing during sleep. Tongue tissue moves towards the back of the throat during sleep and thereby blocks the air passages. OSA is therefore commonly accompanied with snoring.
Different invasive and non-invasive treatments for OSA are known. One of the most powerful non-invasive treatments is the usage of Continuous Positive Airway Pressure (CPAP) or Bi-Positive Airway Pressure (BiPAP) in which a patient interface, e.g. a face mask, is attached to a tube and a machine that blows pressurized gas, preferably air, into the patient interface and through the airway in order to keep it open. Positive air pressure is thus provided to a patient through a hose connected to a patient interface or respiratory interface, such as a face mask, that is worn by the patient. The afore-mentioned long-term use of the patient interface is the result, since the wearing of the patient interface takes place during the sleeping time of the patient.
Examples for patient interfaces are:
nasal masks, which fit over the nose and deliver gas through the nasal passages,
oral masks, which fit over the mouth and deliver gas through the mouth,
full face masks, which fit over both, the nose and the mouth, and deliver gas to both, and
nasal pillows, which are regarded as masks as well within the scope of the present invention and which consist of small nasal inserts that deliver the gas directly to the nasal passages.
The patient interface is usually positioned on the patient's head using some kind of headgear. Wearing a patient interface can be uncomfortable, since for providing an airtight seal between the patient interface and the patient's face, the patient interface has to be worn tightly on the face. Further, the patient interface may comprise a forehead support. Such a forehead support is often designed as a pad that touches the forehead of a patient during use. It is often included in order to relief the pressure of the patient interface on the nose bridge.
In order to remedy that the wearing of the patient interface is uncomfortable, US 2008/0314390 A1 suggests to equip a facial mask with an automatically adjusting forehead support. This forehead support is adapted to be movable between two positions and includes a biasing mechanism that urges the forehead support in the second position. Thereby a more comfortable wearing of the mask shall be achieved.
However, as a part of such a patient interface being uncomfortable, the tightly wearing of the patient interface on the face may result also in pressure points and red marks once the patient interface is removed.
In another aspect, even if the patient interface is tightly mounted on the patient's face initially, the patient interface may start leaking during the sleeping time, thereby reducing the effectiveness of the medical treatment. When a patient turns to his side, the pillow may shift the patient interface relatively to the face. This can result in leakage of the patient interface. Another cause for leakage may be the relaxation of facial muscles as soon as the patient falls asleep. As a consequence, the stiffness of the facial surface changes and induces leakage of the patient interface. Therefore, there is a need for an automatic re-adjustment of the patient interface due to a shifted position of the interface and a muscle relaxation during the sleeping time of the patient.
In a further aspect, each patient's face features an individual facial contour. As an example, the size of the nose can vary from face to face. If the patient interface is only offered in one standard size, the large-nosed patients feel more seal pressure and less comfort, since the large nose stretches the seal more than a smaller nose. As a remedy, it is known to manufacture custom patient interfaces. However, this requires expensive and time consuming calibration work.